1. Technical Field
The present invention relates to a print apparatus.
2. Related Art
A print apparatus such as a printer generates binary output gradation data by screen-processing input gradation data having a multiple gradation value for each pixel. Then, in a print engine, an image is formed in accordance with the generated output gradation data.
As the screen processing, a processing by a clustered dot-type dither method called multi-level dither method has been known. In a common multi-level dither method, dots are formed in a cell such that an area of dots (halftone dots) becomes larger from a center of the cell as an input gradation value is increased. Note that the cell is formed by a plurality of pixels.
However, in the screen processing by the multi-level dither method, there is the following problem. That is, a fine line is broken, or jaggy is generated on edge portions of a character or a line, in particular, at a low density.
In order to solve the problem, a method in which edge detection is performed on an input image and different image processings are performed on edge pixels and non-edge pixels has been proposed (for example, JP-A-2009-100228).
In the method, a screen processing by a clustered dot-type multi-level dither method which is similar to the existing method is performed on the non-edge pixels and a filtering processing in consideration of visual characteristics is performed on the edge pixels. With this, image quality is improved.
However, when the edge pixels and the non-edge pixels cannot be separated from each other accurately even by using the above method, an expected effect of image quality improvement cannot be obtained.
For example, when color information is canceled in order to simplify (speed up) a processing even if a color of the edge pixels is different from a color of the non-edge pixels in terms of color values, the edge pixels and the non-edge pixels cannot be separated from each other accurately in some case (for example, when brightnesses thereof are closer to each other).
Further, the edge pixels and the non-edge pixels can be also separated from each other accurately without canceling the color information thereof. However, in such a case, load onto hardware or software is increased. For example, a buffer size is increased or a processing speed is lowered.